1. Field of the Invention
The present invention relates to an ink jet recording head and an ink jet recording apparatus which perform recording by ejecting (discharging) an ink toward a record material. The invention is applicable to systems such as a word processor having a facsimile and printer section equipped with a printer, a copying machine and a communication system, which conducts the recording on record mediums such as paper, yarns, fibers, dishcloth, leather, metals, plastics, glasses and ceramics, and additionally applicable to an industrial recording apparatus involving a composite combination thereof with various types of processing units. In the invention, the xe2x80x9crecordingxe2x80x9d signifies not only that meaningful images such as letters and figures are recorded on a record medium, but also that unmeaningful images such as patterns are recorded thereon.
2. Description of the Related Art
An ink jet recording apparatus is made to form an image of an ink dot pattern by supplying an ink to an ink jet recording head (which will be referred to hereinafter as a head) and by driving an ink droplet ejecting means such as a piezo device or an electrothermal converter, situated on the head, in accordance with image data.
In the case of color printing, a head is provided, for example, for each of yellow, Magenta, cyanogen and block inks, and in the case of a scanning type recording apparatus, these heads are mounted on a carriage which reciprocates along a record medium in predetermined directions. In a color recording apparatus, the heads for the respective colors are disposed in carriage moving directions (main scanning directions).
There is a problem which arises with the above-mentioned construction, however, in that the number of heads for the color recording increases so that the cost of the head unit increases and, additionally, so that the recording apparatus tends to increase in size.
FIG. 11 is a perspective view showing, as one example, a group of heads of a conventional ink jet color recording apparatus using inks different in density or consistency.
In this recording apparatus, a black (BK) ink head 311BK, a first cyanogen (C1) ink head 311C1, a second cyanogen (C2) ink head 311C2, a first Magenta (M1) ink head 311M1, a second Magenta (M2) ink head 311M2 and a yellow (Y) ink head 311Y are arranged in parallel.
In the case of a head group having such a construction, since there is a need for the positional accuracy of adjacent nozzles of the heads to be set up on the order of microns, its manufacturing process becomes complicated, and additionally, installation of a head for each of ink colors leads to a relatively high head cost and makes difficult the size reduction of the head unit itself. Accordingly, the recording apparatus itself tends to increase in size and additionally to become costly.
In addition, since the plurality of heads are in a separated condition, there is a need to prepare, for each of the heads, an ink suction/pressurization receiving means for removing bubbles in the interiors of the nozzles or for recovering the ink from the increasing viscosity due to its being left for a long time.
One possible solution to these problems may be that a plurality of ink jet recording heads are formed integrally on the same substrate and disposed along the main scanning directions for conducting multivalued printing.
However, the point to be improved in the recording apparatus in which each of four color inks, namely, yellow, Magenta, cyanogen and block inks, existing in the main scanning directions has different densities is that four colorsxc3x97two heads, namely, inks of eight colors., are necessary.
Meanwhile, it was found that yellow and block images are sufficiently expressible in color appearance through printing density or the like, and do not require variation of the ink density. On the other hand, the ink density has relatively great influence on color images based on Magenta and cyanogen in color appearance. Hence, a multivalued color recording apparatus using the needed minimum number of inks is desirable.
Accordingly, a recording apparatus can be designed such that one type is used as each of yellow and black inks and two types are taken as each of Magenta and cyanogen inks, that is, six color inks are put to use.
FIG. 12 is an illustration of one example in which nozzles for six colors are disposed separately in two heads.
In FIG. 12, a group of nozzles comprising a nozzle group 400Y for ejecting an yellow ink, a nozzle group 400M1 for ejecting a first Magenta ink and a nozzle group 400C1 for ejecting a first cyanogen ink is formed in a recess section 357 made in a face 356 of an orifice plate 403 attached to a head 301A.
In addition, a group of nozzles comprising a nozzle group 400BK for ejecting a black ink, a nozzle group 400M2 for ejecting a second Magenta ink and a nozzle group 400C2 for ejecting a second cyanogen ink is formed in a recess section 357 made in a face 356 of an orifice plate 403 attached to a head 301B. Still additionally, in the case of an apparatus employing different ink densities, since the dot formation order or time lag has influence when different inks are mixed to produce a secondary color, it is preferable that the different inks to be mixed are adjacent to each other in the main scanning directions of printing.
The disposition shown in FIG. 12, however, creates the following problems if two heads are disposed in the main scanning directions of printing.
That is, if the two heads are disposed in parallel as shown in FIG. 12, the yellow nozzle group and the black nozzle group assume an adjacent condition, and the two-color printing are required to be conduct simultaneously.
At this time, it was found that two types of inks interfere with each other on the record material to come to the boundary portion between images, that is, the so-called bleeding occurs, which degrades the print quality. Particularly, it can occur remarkably between yellow and black between which a great color difference exists.
Therefore, it is considered that nozzle groups discharging two different inks are disposed so as not to be adjacent to each other in the main scanning directions. That is, as shown in FIG. 13, a first nozzle of a nozzle group 200M1 of a head 301A and a first nozzle of a nozzle group 200M2 thereof are placed on a line Axe2x80x94A.
However, in this case, a wasteful space 340 comes about in the head section so that the head itself increases in size to cause the size increase of the recording apparatus itself.
One possible solution to these problems would be that the wasteful space is removed from the head in FIG. 13 as disclosed in Japanese Unexamined Patent Publication No. (HEI) 7-132619. That is, as shown in FIG. 14, the head 301A and the head 301B are disposed and density-different inks are used to enable high-quality multivalued color recording, and additionally, the nozzles of adjacent nozzle groups are disposed in a state shifted substantially by xc2xd of a nozzle pitch from each other in directions different from the main scanning directions to double the resolution for formation of a color image with a high gradation.
Furthermore, as shown in FIG. 15, the employment of a head 391B having a nozzle group holding only a black ink can accomplish higher-speed printing of a black image. Additionally, in this case, by using a B section of a nozzle group of a head 391 for ejecting a black ink, a nozzle group 490Y of a head 391A for ejecting an yellow ink, a nozzle group 490M thereof for ejecting a Magenta ink and a nozzle group 490C thereof for ejecting a cyanogen ink, a color image is also printable.
Secondly, a description will be given hereinbelow of an orifice plate 403 with nozzle groups in the aforesaid heads.
FIG. 16 is a perspective view showing a conventional orifice plate 403, FIG. 17 is a cross-sectional view showing the orifice plate 403, taken along a line Bxe2x80x94B, and FIG. 18 is a cross-sectional view showing the orifice plate 403, taken along a line Exe2x80x94E.
In a face 356 of the orifice plate 403, there is made a recess section 357 which has a plurality of nozzles arranged therein.
The recess section 357 has a recessed configuration comprising a curved surface formed by a combination or connection of a first surface 351 and a second surface 352 at the deepest portion Lxe2x80x2 of the recess section 357, and further comprising a third surface 353 and a fourth surface 354 provided on both sides of this curved surface.
In comparison with the second surface 352, the first surface 351 forms a curved surface having a relatively steep inclination, whereas, in comparison with the first surface 351, the second surface 352 constitutes a gentler curved surface. Accordingly, the deepest portion Lxe2x80x2 where the first surface 351 and the second surface 352 are combined is positioned above a nozzle 400, that is, on the upstream side thereof in an arrow W direction indicative of a running direction of a blade 319 for wiping out an ink attached onto the recess section 357.
Of heads manufactured so far, as shown in FIG. 17, there is a recording head using a member in which formed integrally are an orifice plate 403 having a number of common ink droplet discharging nozzles 400 and a top board 100 having groove portions forming ink passages corresponding respectively to the nozzles 400.
In an ink jet recording apparatus employing such a recording head, there is a case that wet ink is attached onto the recess section 357 due to ink mist occurring when an ink is ejected from the recording head or due to satellite ink occurring at the refilling of the ink. Additionally, for example, when the ink is sucked from the nozzle 400 for restoration processing, the ink left at the suction can be attached to the recess section 357.
Therefore, a restoring unit has been provided to remove such attached ink from an ejection surface. This restoring unit is principally made up of a suction device for discharging ink forcedly from the nozzle 400 and a wiping device for wiping and cleaning the recess section 357.
For example, the wiping device is designed to make a blade 319, made from an elastic material or the like and shown in FIG. 19, come directly into contact with the face 356 and the recess section 357 and to make the blade 319 move relatively to slide on or rub against the face 356 and the recess section 357, thereby cleaning the plurality of nozzles 400 and the portions around them for securing the ejection stability.
However, it was found that a construction in which a head 301A and a head 301B are disposed in a state shifted from each other as shown in FIG. 19 can create a problem when the blade 319 wipes and cleans (wiping) the face 356 and the recess section 357.
That is, since there is a need for the face of the orifice plate composed of a conventional top board with grooves to be as thin as possible in the vicinity of the nozzles but for the entire face to be thick sufficient to increase its strength, naturally, the entire face does not have a flat configuration but it has a recess portion.
In addition, in order to prevent the dries of the nozzles of the head, there is a need for the face to have a configuration to be covered with a cap installed commonly in a printer body; therefore, it is preferable that, in the face having the aforesaid recess portion, a part which comes into contact with the cap exists on the plane including a surface other than the recess portion.
In consequence, as shown in FIG. 17, the recess section 357 is formed at a substantially central portion of the entire face 356.
Meanwhile, in recent years, with the increasing requirements of high image quality, high density and high resistance to light, the versatility of ink in kind has taken place, so that there has existed an increasing need to handle dispersive pigment based inks in addition to a conventional water soluble dye based inks.
If a pigment ink is used in a cartridge with a conventional configuration, when the residual ink on an orifice plate is wiped out by a blade, ink accumulation occurred in the vicinity of the third surface 353 and the fourth surface 354 of the recess section 357 as shown in FIG. 16.
In general, the pigment-based ink has large molecules and has a fixedly attaching property.
For this reason, if some ink is yet left on the orifice plate after being wiped off, there is a possibility that the reception of the ink ejected becomes unstable.
In addition, the pigment ink left after wiped off can enter the nozzles due to the subsequent wiping operation by the blade, thereby causing an ejection-impossible condition.
Still additionally, in addition to the ink accumulation 500 shown in FIG. 16, the residual or leavings after the wiping can also occur slightly around the nozzles 400, which can cause the deflection of ink ejected or the ejection-impossible condition.
A conventional means to solve this problem relates to the improvement of the wiping way using a blade placed in the printer body. Since the ink used so far has been an dye ink, this conventional means has worked successfully. However, when a pigment ink is used for a higher resistance to light and higher concentration, further improvement becomes necessary.
Moreover, in addition to the aforesaid problems arising with the recess section, the following problems will arise.
That is, when sliding on the face 356 and the recess section 357, the blade 319 also slides simultaneously on a chip tank 302A and a chip tank 302B which have a flow passage for supplying the ink into a nozzle liquid chamber. The repetition of this operation can cause the ridgelines of the chip tanks 302A and 302B along the main scanning directions to damage the points A to D of the blade 319 as shown in FIG. 19. If the wiping is done in this state, the point B of the blade 319 can induce the ink leavings on the head 301A while the point C thereof can induce the ink leavings on the head 301B; whereupon the nozzles 400 become a wet condition to lead to record contortion or ejection failure.
Accordingly, it is a first object of the present invention to provide an ink jet recording head, an ink jet cartridge and an ink jet recording apparatus which can reduce the ink leavings or residual after wiping.
A second object of this invention is to provide an ink jet recording head, an ink jet cartridge and an ink jet recording apparatus which are capable of maintaining an excellent condition even if a pigment ink is put to use.
A third object of this invention is to provide an ink jet recording head, an ink jet cartridge and an ink jet recording apparatus which are capable of accomplishing less damages to a wiping blade.
For achieving these objects, in accordance with this invention, there is provided an ink jet recording head comprising a flat plate section having a recess section in its surface and an orifice plate having a plurality of openings made to eject a liquid and disposed linearly to be grouped in the recess section, with the surface of the flat plate section being cleaned by a cleaning member movable relative to the flat plate section in a direction perpendicular to a direction of the disposition of the ejecting openings in a state brought into contact with the surface of the flat plate section, wherein the recess section includes a combined curved surface made in a manner that a first curved surface having a first curvature and a second curved surface having a second curvature smaller than the first curvature are combined at a position corresponding to the deepest portion of the recess section so that the first curved surface is on the upstream side of the second curved surface in a cleaning direction of the cleaning member and made to extend in the disposition direction of the ejecting openings and further includes two inclined surfaces formed at both end portions of the combined curved surface to develop from the surface of the flat plate section in a state respectively separated from both end portions of the grouped ejecting openings existing in the vicinity of the deepest portion.
In an ink jet recording head thus constructed according to this invention, since the ejecting opening group is formed in the vicinity of the deepest portion of the recess section made in the orifice plate, the depth of the recess section assumes the minimum needed, thus making no sharp angle with respect to first and second inclined surfaces forming both end portions of the combined curved surface. Accordingly, the angles made at areas connecting the combined curved surface and the first and second inclined surfaces become blunt so that the liquid is hard to stay after the cleaning by the cleaning member.
It is also appropriate that the ejecting opening group is formed on the downstream side in the cleaning direction with respect to the deepest portion, that the surface in which the ejecting opening group is made is a general plane formed substantially perpendicularly to directions of liquid ejection by the ejecting openings, or that each of areas existing connectively between the first curved surface, the second curved surface, the two inclined surfaces and the general plane is formed as a smooth curved surface.
It is also possible that the ink jet recording head according to this invention includes an equipment body formed integrally with the orifice plate in a state where the surface of the flat plate section is used as one of component surfaces.
It is also possible that, in the equipment body, a radius of a curved surface formed on a first ridgeline portion defined by a surface, with which the cleaning member comes initially into contact with at the relative movement of the cleaning member, and the surface of the flat plate section to extend in a direction perpendicular substantially to the relatively moving direction of the cleaning member is below 0.1 mm, or that, in a second ridgeline portion defined by a surface including the recess section and a surface of the equipment body substantially perpendicular to the surface including recess section and substantially parallel with the relatively moving direction of the cleaning member, the radius of a curved surface formed on a portion on which the cleaning member slides at the relative movement is equal to or more than 0.2 mm.
Furthermore, it is also acceptable that the radius of a curved surface formed on a corner portion of the equipment body defined by the first and second ridgeline portions is equal to or more than 0.2 mm, that the starting position of the curved surface of the second ridgeline portion is separated by more than 0.1 mm from the ejecting opening closest to the second ridgeline portion, or that the liquid is a pigment ink.
Still furthermore, it is also appropriate that the ink jet recording head according to this invention is equipped with an electrothermal converter for generating thermal energy to be used for ink ejection, or that the ink jet recording head is of a type that an ink is ejected from the ejecting openings utilizing the film boiling occurring in the ink due to thermal energy from an electrothermal converter.
An ink jet cartridge according to this invention comprises the ink jet recording head according to this invention and a liquid container for holding an liquid to be supplied to the ink jet recording head.
An ink jet recording apparatus according to this invention comprises the ink jet cartridge according to this invention and a record medium conveying means for conveying a record medium onto which the liquid ejected from the ink jet recording head is adhered for recording.
In addition, the ink jet recording apparatus comprises the aforesaid ink jet recording apparatus according to this invention and a cleaning member moved relatively in a direction perpendicular to an arranging direction of ejecting openings while being brought into contact with a surface of a flat plate section of the ink jet recording head to clean the surface of the flat plate section.
According to this invention, since the ejecting opening group is formed in the vicinity of the deepest portion of the recess section made in the orifice plate, the depth of the recess section becomes at the minimum needed so that the angles made with respect to the first and second inclined surfaces forming both the end portions of the combined curved surface do not become sharp. Accordingly, the angles of the areas between the combined curved surface and the first and second inclined surfaces become blunt so that the liquid is hard to stay, and even if a pigment ink, easy to fix, is used, it is possible to maintain an excellent ink ejection condition for a long time.
Moreover, the first ridgeline portion, the second ridgeline portion and the corner portions of the equipment body formed integrally with the orifice plate are made to have a radius R, which enables less damage to the cleaning member and secures the certain cleaning of the recess section.